Patent Literature (PTL) 1 discloses a configuration related to a storage system having multiple SAS (Serial Attached SCSI) expanders that serve as interfaces for coupling hard disk drives and that are cascade-coupled to a storage controller. This configuration aims to obtain extensibility and high availability.
PTL 2 discloses a computer system that includes a computer, a first storage device coupled to the computer, and a second storage device externally coupled to the first storage device. The first storage device provides a first storage area to the computer, and the second storage device includes a second storage area corresponding to the first storage area. To prevent operations from stopping due to a path failure, this computer system determines whether or not a failure has occurred in at least one of first to fourth paths; selects a path used for access to the first storage area or the second storage area, based on a result of the determination; and sends, through the selected path, a request to access the first storage area or the second storage area.